The long-term objective of this proposal is to understand the biochemical basis of the three major forms (infantile, late infantile, and juvenile) of neuronal ceroid lipofuscinosis (NCL) or Batten disease. This will permit precise diagnosis of NCL, detection of heterozygotes, and facilitate new forms of therapy for this devastating neurodegenerative disease which causes retinal degeneration and loss of all neurofunctions in 3000 children each year. We will test a hypothesis that a deficiency of lysosomal phospholipase A1 (PLA1) can lead to the biochemical and pathological changes observed in Batten disease. To achieve this, we will first purify the PLA1 from human tissue and determine the conditions for optimum activity and substrate specificity. We will determine PLA1 activity in tissue homogenates prepared from patients with Batten disease to verify our initial data which suggests a marked deficiency. We will assay activity in immortalized lymphocytes from obligate NCL carriers to verify that PLA1 is the primary defect by showing 50% of normal activity in these carriers. We will then prepare polyclonal antibody to PLA1 and use it to study synthesis, processing, and subcellular localization of PLA1 in normal versus mutant cells. Because of the importance of animal models in devising therapy for storage diseases, we will attempt to confirm the PLA1 deficiency in English Setters with NCL, and use tissue from the obligate carriers to devise a reliable carrier test. Finally, in order to understand the pathogenesis of NCL, we will investigate how a lysosomal PLA1 deficiency can give rise to a "functional protease deficiency", involving primarily central system neurons and pigmentary epithelial cells of the retina. We will attempt to recreate the disease in vitro with the proposed pathogenic agent 4-hydroxynonenal, study two patients with apparent primary cathepsin H deficiency and clinical symptoms resembling NCL, and prepare [125I]labeled rhodopsin, and the putative major storage peptide in NCL (the C-subunit of mitochondrial ATP synthase) for use in in vitro assays with NCL tissue.